Scientists have developed an immune-suppressing drug regimen that, when used in combination with genetically-modified pig organs, has enabled the longest-to-date survival of a heart transplant from a pig to a primate (baboon). Their study, published online in Nature Communications, could lead to expanded use of xenotransplantation.

Read also: Molecular profiling of kidney transplants might catch rejection earlier 

One of the major obstacles to successful xenotransplantation is a strong immune system response of the organ recipient, which can lead to organ rejection and failure.  To overcome this problem, researchers have explored a variety of strategies to prevent or minimize rejection, including modifying the organ donor’s genes and developing novel immune-suppressing drugs for the organ recipients.

In the current study, scientists developed a novel immune-suppressing drug regimen that includes a key antibody, called anti-CD40 antibody, that holds promise for resisting attack by the immune system.  The researchers obtained a group of pigs genetically modified to have high immune system tolerance and then transplanted the pig hearts into a group of five baboons. In each case, the pig heart did not replace the baboon heart but was instead connected to the circulatory system of the baboon, while the baboon’s own heart continued to pump blood.

Read also: Financial incentives for organ donation a polarizing issue, but it’s time to test the waters 

Using the new immune-suppressing drugs, the genetically modified pig hearts survived for up to 945 days (over two and a half years) in the baboons. This milestone shattered previous records of pig-to-primate heart transplant also achieved by this group of researchers over past five years. The novel immune-suppressing drugs were a key to the transplant’s success, the scientists said.